This invention relates to distributed amplifier circuit design, more particularly to the application of filter synthesis techniques for controlling distributed amplifier characteristics.
Distributed amplifiers are common circuits found in numerous applications such as telecommunications, sensing, and instrumentation. A principal feature of distributed amplifiers is that it provides broad frequency amplification with nearly uniform gain and delay response. Synthesis of these amplifiers has been primarily based on synthetic transmission line construction, i.e. uniform unit cells. This structure poses several disadvantages, the two most significant being large gain ripple and large group delay variation as the signal frequency approaches the band-edge. The effect of these performance limitations is significantly distorted signals, e.g. pulse waveforms. Reducing or eliminating gain and/or delay variations maintain the integrity of the signal as it passes through the distributed amplifier. To date, the primary approach to improving the response of distributed amplifiers has been to reduce the size of the uniform sections. This is an incomplete approach that also degrades circuit performance. Numerous other improvements have also been documented, but none address the problems of gain and delay variation. As the speed of digital signal transmission increases and higher frequencies are used, the detrimental effects of gain and delay variations increase as well.
Accordingly, there is a need for a distributed amplifier that produces a more uniform gain and delay over a wide bandwidth.
The present invention describes the method and system of applying filter synthesis techniques to distributed amplifier design. The method for synthesizing a distributed amplifier comprises the steps of determining an appropriate filter design characteristic, computing inductor and capacitor values, converting the equivalent values into a distributed amplifier with response characteristics that mirror that of the chosen filter.
Applying filter synthesis techniques to distributed amplifier design results in predictable amplifier response characteristics. Filter synthesis techniques are used to design filters with controllable characteristics such as gain, cut-off frequency, and roll-off slope. Depending on the desired filter characteristics, appropriate inductor and capacitor sizes can be determined. Transferring these chosen inductors and capacitors sizes to the distributed amplifier results in amplitude and phase responses that behave like the preferred embodiment or prototype filter. Advantageously, this method of utilizing filter-based L-C (Inductor-Capacitor) sizes provides improved performance of the distributed amplifier; e.g. minimal amplitude variation, minimal delay variation, controlled roll-off characteristics.